The present invention relates to a lever switch, and more particularly to a lever switch composed of a plurality of microswitches arranged along a straight or circular line and having respective pushbuttons, and a plurality of rolling bodies such as balls disposed in facing relation to the pushbuttons, the rolling members being selectively depressable in response to the actuation of a lever member for energizing and de-energizing a desired microswitch.
Various switches are widely used for making and breaking electric circuits through angular movement of lever members. A typical example of conventional lever switches of the type described is illustrated in FIG. 1. The illustrated prior lever switch includes a base 2 made of an electrically insulating material and supporting holders 4 bent at about 90.degree. and erected thereon. Fixed contacts 6 are each mounted on one flat portion of each of the holders 4, while a bolt 8 is threaded through the other flat portion of each holder 4 and joined to a conductor 10. The holder 4, contact 6, bolt 8, and conductor 10 jointly constitute a fixed contact assembly 12, and a plurality of such fixed contact assemblies 12 are mounted on the base 2 in 90.degree.-spaced positions. A slide 14 is disposed between each pair of fixed contact assemblies 12. the slide 14 comprises a roller 16 and a support 18 on which the roller 16 is rotatably supported, the support 18 being mounted centrally on a plate member 20. The plate member 20 has movable contacts 22a, 22b on its opposite ends and is resiliently supported by compression coil springs 26a, 26b extending from a support base 24.
The roller 16, support 18, plate member 20, movable contacts 22a, 22b, and springs 26a, 26b jointly serve as a movable contact assembly 28, and a pair of such movable contact assemblies 28 is mounted on the base 2. The rollers 16 of the movable contact assemblies 28 are positioned in mutually confronting relation to each other. Between the rollers 16, 16, there is disposed a cam 32 having two semicircular recesses 30a, 30b and rotatably supported by a shaft 34 coupled to a lever, not shown.
Operation of the switch thus constructed will be described. Under normal or inoperative condition, the peripheral surface of the cam 32 is pressed against the peripheral surfaces of the rollers 16, 16 to push the plate members 20 of the movable contact assemblies 28 toward the ends of the base 2 against the resilience forces of the compression coil springs 26a, 26b. The movable contacts 22a, 22b are therefore held out of contact with the fixed contacts 6, 6, and electric circuits connected to the switch are kept open.
When the non-illustrated lever is turned, one of the rollers 16 pressed against the peripheral surface of the cam 32 rolls and enters into the recess 30a. At this time, the compression coil springs 26a, 26b under compression are expanded under their own resiliency to displace the movable contacts 22a, 22b on the plate member 20 into contact with the fixed contacts 6, 6, allowing an electric current to flow from one of the conductors 10 to the other in the direction of the arrows. Thus, one of the electric circuits (which is the upper electric circuit in FIG. 1) is closed.
Continued rotation of the lever causes the other electric circuit (which is the lower electric circuit in FIG. 1) to be closed, and also causes the upper electric circuit to be opened.
With the above structure, however, the plate member 20 is angularly displaced unless the movable contacts 22a, 22b are substantially translated under the resilient forces from the pair of coil springs, and if the plate member 20 is angularly displaced, then the movable contacts 22a, 22b fail to contact the fixed contacts 6, 6. Therefore, the resilient forces of the paired coil springs have to be equal to each other. If the coil springs become unable to to produce sufficient resilient forces due for example to a deposit of dust, then the electric circuits cannot be closed as desired.
The cam and movable contacts are mostly fabricated as molded parts. If these molded parts are dimensionally varied, then no sufficient and reliable operation to open and close the electric circuits can be achieved. Since the rotating cam and the other movable parts are disposed in close proximity to the contacts, if one of these parts is damaged or broken, a malfunction will result or no circuit opening and closing operation will be effected at all. The conventional construction therefore fails to sufficiently meet the demand of recent control apparatus which employ many semiconductor circuit devices for controlling operation at a low voltage and a small current.